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  1. #1
    Senior Member JonnyV's Avatar
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    Brazing steel tubes into stainless steel lugs?

    Hey guys, I'm getting ready to piece together my first frame build. I've done brazing before, I've worked with silver solder. But I'm not too 100% sure about this so I want to ask you guys. Is it ok to braze steel tubes to stainless steel lugs? I know not to do something like braze aluminum to stainless, that's just asking for trouble. But would I be inviting the same trouble with the steel to stainless?
    Some people are just like Slinky's. Not really good for anything but they bring a smile to your face when you push them down the stairs.

    2012 Fuji Altamira 1.0

  2. #2
    framebuilder
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    Wait until you have more experience before trying to make a frame with stainless lugs and regular steel tubes. I don't let my framebuilding class students use stainless steel lugs on their first frame for good reason. And this is after a through explanation of brazing principles and a demonstration of exactly what motions are required. Stainless lugs are much more difficult to braze than regular steel and don't tolerate mistakes. They don't transfer heat as well (meaning your heat application has to be more even) have a smaller heat window (meaning that the joint temperature needs to be higher but can't tolerate being too high), it requires more stringent cleaning and the surface corrupts more easily when overheated and can't recover. A mistake requires taking the joint apart to do it over. Also while stainless lugs can be brazing with normal 56% silver and standard white flux (like Gasflux Type U), I would recommend 50N silver with either Cycle Design's Stainless Light flux or Gasflux's Type G (it is active to 1700 degrees instead of the standard 1600).

  3. #3
    Randomhead
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    just to second what Doug said, if you try to use stainless lugs for your first frame you are setting yourself up for failure. We don't want that.

    After decades of brazing, the first time I tried brazing stainless it was a disaster. Very annoying. Now I make sure I'm in a calm state of mind before I start. Stainless goes from being too cold to being up to temperature very fast and before you know it there is un-brazeable cruft everywhere.

  4. #4
    Senior Member JonnyV's Avatar
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    Lol Ok, this is great to know. I have no problem learning from others mistakes. I really liked the Shogun style lugs from Nova but I'll see whatelse they've got. Thanks for the info guys. If there's anything else you think I need to know, please let me know.
    Some people are just like Slinky's. Not really good for anything but they bring a smile to your face when you push them down the stairs.

    2012 Fuji Altamira 1.0

  5. #5
    coprolite fietsbob's Avatar
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    Silver solder/braze runs thin, and so lug over tube has to be a tight fit.

    brass fills gaps better, I am still, occasionally, riding the stamped steel 'prugnut' lug build I did in the 70's.

  6. #6
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    The above advice is certainly sound and you should take it.

    Having said that, I ignored it completely and did my first build with stainless, lugs and silver and it worked out OK.

    Another thing to add to the case for the negative- if your intention is to do stainless so you can polish the lugs a la Llewellyn, you should be aware that the man has many years of experience and the patience of Job to do what he does. I found getting a decent brushed finish required many hours of incredibly tedious finishing work. To get a bright polished finish would be beyond my pain tolerance.

  7. #7
    Senior Member JonnyV's Avatar
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    Quote Originally Posted by Mark Kelly View Post
    The above advice is certainly sound and you should take it.

    Having said that, I ignored it completely and did my first build with stainless, lugs and silver and it worked out OK.

    Another thing to add to the case for the negative- if your intention is to do stainless so you can polish the lugs a la Llewellyn, you should be aware that the man has many years of experience and the patience of Job to do what he does. I found getting a decent brushed finish required many hours of incredibly tedious finishing work. To get a bright polished finish would be beyond my pain tolerance.
    Yeah, that was the idea. The lugs I found from Nova are already polished. I'd probably have to go back over them when finished though. I'd be fine with that. However, I found they have the same design in mild steel so I'm going that direction with the first frame.
    Some people are just like Slinky's. Not really good for anything but they bring a smile to your face when you push them down the stairs.

    2012 Fuji Altamira 1.0

  8. #8
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    I seem to recall Darrell (Llewellyn) McCulloch saying that pre-polishing wasn't worth the effort because the flux etches the polished surface so you have to polish it again anyway.

    I haven't done any polished lugs, as previously stated I don't have the pain tolerance to try and I prefer the brushed finish with my wood main tubes anyway.

  9. #9
    semi-retired framebuilder
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    Jonnyv, how many test joints have you brazed? As in real tubing in a real lug, properly mitered then brazed, then chopped in half with a hacksaw to look inside? I'd recommend minimum half a dozen test joints and ideally more like 10+, before you set torch to a real frame. Unless, of course, you intend to chop up frame number one, but I know the temptation is to build it and ride it. Just curious, of course.

    Mark Beaver
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  10. #10
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    For a starter frame, you may want to go with a simpler lug shape. I was advised to stay away from the fancy lug shapes for a while. I'm only on frame 7 so I hope somebody with more experience will chime in on this but a simple long point lug will be easier to braze and then clean up. It might be hard to flow the filler without overheating the smaller parts of those lugs. Until you learn to get clean shorelines with no globs or voids, you will not be happy with the results and clean up will leave you hating life.

  11. #11
    Randomhead
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    I've heard that the main advantage to pre-polished lugs is that the casting house finds out there are issues with the casting prior to shipping the part.

  12. #12
    Senior Member JonnyV's Avatar
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    Quote Originally Posted by busdriver1959 View Post
    For a starter frame, you may want to go with a simpler lug shape. I was advised to stay away from the fancy lug shapes for a while. I'm only on frame 7 so I hope somebody with more experience will chime in on this but a simple long point lug will be easier to braze and then clean up. It might be hard to flow the filler without overheating the smaller parts of those lugs. Until you learn to get clean shorelines with no globs or voids, you will not be happy with the results and clean up will leave you hating life.
    This seems like a good idea. I like the look of just about all lugs so I'm fine with the long point lugs and I had considered the issue of heating the small points of the fancies, I think I'd be ok, but I'd rather be sure. I'll look into a long point lug set.

    As for the question about how many test brazes...0. My intent wasn't to ride it out on the road until I've got a good number of "miles" on the trainer and rollers to see how the joints handle it before it would hit the road. Is there a source for super cheap lugs for the test/practice brazes?
    Some people are just like Slinky's. Not really good for anything but they bring a smile to your face when you push them down the stairs.

    2012 Fuji Altamira 1.0

  13. #13
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    Super cheap practice lugs are hard to find. Stamped lugs from Nova are stiill going to cost $20 a set. You can buy tubing from Aircraft Spruce to practice on though. If you buy two tube sizes that are 1/8" different diameter and the bigger tube has .058 wall thickness, they will fit together like lugs and tubes. Cut them, shape them, braze them and then hack them apart to see how you did. Good practice for both mitering and brazing.

  14. #14
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    Quote Originally Posted by Mark Beaver View Post
    Jonnyv, how many test joints have you brazed? As in real tubing in a real lug, properly mitered then brazed, then chopped in half with a hacksaw to look inside? I'd recommend minimum half a dozen test joints and ideally more like 10+, before you set torch to a real frame. Unless, of course, you intend to chop up frame number one, but I know the temptation is to build it and ride it. Just curious, of course. Mark Beaver Halifax, NS
    Beav +5 on that; I would recommend the nooby do a dozen trial joints of the type at the headtube, at least a couple each of the seattube/toptube junction, and at least a couple bottom brackets. After each trial joint recommend letting it cool completely and then put it on the bandsaw to cut it into at least 2 pieces for examination under a 5X magnifier.

    The real issue I see with doing a full frame before cutting it up for examination is that a mistake in the first joint of the frame will probably be repeated throughout leaving the nooby to waste an entire expensive tubeset, a lugset, dropouts and a bunch of stick and a lot of gas when a series of trials on cheap scrap bits would have induced the requred learning much sooner and at minimal cost. When the technic and experience is there, that 1st tubeset and lug set are still there ready to be used productively.

    My original mentor made it a firm point that nothing would be built for riding until a student ran all the way through two full 5 gal buckets of trimmed off tube nubbin's and his discarded lug bits. That was a lot of trial joints...but it probably resulted in the lessons being more deeply seated. Every trial joint was closely examined before doing the next one. He wouldn't even let a student look at the key to the cabinet where he kept the seldom used silver.
    /K

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